Asset support in pie format

[edeustace]

We need to define how assets are supported in the pie format.

Scenarios:

We may want to add an asset to the pie itself:

   pie/
      img.png

Then in the component:

    this.innerHTML = '<img src="???"></img>';

Or in less/css:

   .my-class{
     background-image: url('....'); 
   }

The content of the pie may contain images:

{ 
  choices: [
    { label: '<img src="???">' }
  ] 
}

So the questions are:

• what are the rules by which you can load an asset into a pie
• what happens if the pie and the config have an image of the same name?
• are images in the config outside the scope of the pie?
• do we bake in all images or bundle them?